1. Technical Field
A system and method for controlling a multi-phase DC-DC converter.
2. Background Art
A multi-phase DC-DC converter (MPC) includes a DC-DC converter with multiple phase-legs connected in parallel. Connecting the phase-legs in parallel allows the current flowing through the MPC (hereinafter “inductor current”) to be distributed between the phase-legs. Distributing the inductor current between the phase-legs provides a number of benefits, particularly for automotive power systems. Consequently, the MPC has gained increasing attention in many automotive applications as demands for automotive power systems have increased.
With reference to FIG. 1, a 2-stage multi-phase DC-DC converter 10 has a first phase-leg 14 and a second phase-leg 16. In addition, the first phase-leg 14 and the second phase-leg 16 are connected in parallel to a battery 12. The first phase-leg 14 has an inductor L1, a switch 51, and a switch S2. The second phase-leg 16 has an inductor L2, a switch S3, and a switch S4. In addition, the 2-stage multi-phase DC-DC converter 10 has a plurality of current sensors 18. The plurality of current sensors 18 sense respective currents flowing through inductors L1 and L2. However, the plurality of current sensors 18 increases the cost, volume, and weight of the 2-stage multi-phase DC-DC converter 10.
With reference to FIG. 2, a first switching signal 21 controls the switch S1 of the first phase-leg 14 (shown in FIG. 1). In addition, a second switching signal 22 controls the switch S2 in the first phase-leg 14 (shown in FIG. 1). In the second phase-leg 16, a third switching signal 23 controls the switch S3 (shown in FIG. 1) and a fourth switching signal 24 controls the switch S4 (shown in FIG. 1).
As shown in FIG. 2, the switching signals 21, 22, 23, and 24 have the same switching frequency and pulse-width modulation (PWM) period. However, switching signals 21 and 22 have a 180° phase shift with respect to switching signals 23 and 24. Since the MPC is a 2-stage converter, the 180° phase shift between switching signals 21 and 22 and switching signals 23 and 24 may reduce the amount of ripple current in the battery 12 or a capacitor (not illustrated). The capacitor may be in parallel with the battery 12, the Vdc, or both the battery 12 and the Vdc.
It is often desirable or necessary to decrease the size and weight of automotive power systems in automotive vehicles to make automotive vehicles more compact, lightweight, and fuel efficient. In addition, it is often desirable or necessary to increase the power density and efficiency of automotive power systems.
With the introduction of the MPC, the distribution of inductor current between the phase-legs provides a number of benefits to automotive power systems. For example, automotive power systems can use smaller components as well as more cost-effective components. Furthermore, automotive power systems can be more compact, lightweight, and inexpensive. In addition, inputs and outputs of automotive power systems typically experience lower ripples. With lower ripples in the automotive power system, filtering losses can be reduced and the filtering system can be reduced in size.
One challenge with distribution of inductor current between phase-legs in the MPC deals with distributing the inductor current in an efficient, reliable, and cost-effective manner. If an improper distribution of inductor current exists between the phase-legs, then the phase-legs may dissipate unequal amounts of heat and lose different amounts of power. As a result, the MPC may experience reduced efficiency and reliability.
An improved MPC control is desired to improve distribution of inductor current between phase-legs in the MPC.